■ DESCRIPTION

The FUJITSU MB3870 is a pulse width modulation (PWM) DC/DC converter IC chip that provides a selection of 1.3 V to 3.5 V output voltages for Pentium®* CPU’s, using a 5-bit input signal information.

The MB3870 utilizes synchronous rectification for high efficiency and features a soft-start/discharge control function for ease in designing power supplies in multi-supply systems, making it ideal for Pentium® II power supply systems.

■ FEATURES

• Highly efficient for using synchronous rectification scheme

• On-chip soft-start/discharge control circuit

• High precision output voltage: ±1.2

• 5-bit, 32-step DAC: 3.5 V to 2.1 V in 100 mV steps

2.05 V to 1.3 V in 50 mV steps

• Frequency range: 100 kHz to 500 kHz using variable resistance (on-chip frequency setting capacitance)

• Standby current: 0 µA TYP

• On-chip PWRGOOD circuit for output voltage state detection

• Timer-latch short-circuit protection circuit, and overvoltage protection circuit for output protection